Arcbound Reclaimer + Showdown of the Skalds + Delif's Cone + Bolas's Citadel

Arcbound Reclaimer

Showdown of the Skalds

Delif's Cone

Bolas's Citadel

How it works

1. Cast Delif's Cone either from your hand by paying 0 or from the top of your library by paying 0 life.
2. Showdown of the Skalds triggers, putting a +1/+1 counter on Arcbound Reclaimer.
3. Activate Delif's Cone by tapping and sacrificing it.
4. Activate Arcbound Reclaimer by removing a +1/+1 counter from it, putting Delif's Cone from your graveyard onto the top of your library.
5. Repeat.

This clever little loop uses Bolas's Citadel to cast Delif's Cone for zero life right off the top of your library, triggering Showdown of the Skalds's chapters to place a +1/+1 counter onto Arcbound Reclaimer. You then sacrifice Delif's Cone to its own ability, allowing Arcbound Reclaimer to spend that newly placed +1/+1 counter to recycle Delif's Cone right back onto the top of your library. Because Bolas's Citadel lets you replay the artifact for free instantly, the cycle resets to generate an infinite loop of artifact sacrifices, enters-the-battlefield triggers, and growing counters.